As one of the most important parts of a seat of a vehicle, in particular of an automobile, backrest is used for supporting the lumbar and back regions of an occupant and for absorbing impact forces applied by the occupant in particular in the event of a crash accident to provide sufficient cushion.
A seat backrest mainly includes a framework and a cushion covering the framework. As a load supporting structure, the framework is traditionally made of a metallic material, such as carbon steel. However, the high density of the carbon steel is not good for reducing weight of the seat and the vehicle. Therefore, the use of carbon steel must be minimized to reduce weight, which limits the size and loading area of the backrest framework. For example, the lower portion and side portions of the backrest framework can only be formed into slats or bars having relatively smaller loading areas, thereby impairing the strength and stiffness and not favorable for absorbing and distributing impact forces. Also, the central support portion of the backrest, as a directly loading part, has to be additionally manufactured into separate spring support members of smaller dimension and greater elasticity and to be assembled onto the framework via additional steps. Generally speaking, the seat backrests currently available as described above suffer from the following drawbacks: heavy weight, imperfect impact energy absorbing effect and comfort, unsatisfactory manufacturability and less freedom of design. In addition, it has been always desirable to design the seat backrest so as to save internal space of the vehicle.
The PCT application WO2010/101874A1 discloses a seat back including a backrest formed of a first polymeric material, a bracket formed of a different material than the first polymeric material and anchored to the backrest, and a reinforcing composite layer formed of a second polymeric material and a plurality of fibers and melt bonded to the backrest. However, the seat back proposed by WO2010/101874A1 is complicated in manufacturing process and has insufficient strength.
The present invention aims to solve one or more of the above and/or other problems in the prior art.